Dehydroxylated Polyvinyl Alcohol Separator Enables Fast Kinetics in Zinc-Metal Batteries

Abstract

Separators are critical components of zinc-metal batteries (ZMBs). Despite their high ionic conductivity and excellent electrolyte retention, the widely used glass fiber (GF) membranes suffer from poor mechanical stability and cannot suppress dendrite growth, leading to rapid battery failure. Contrarily, polymer-based separators offer superior mechanical strength and facilitate more homogeneous zinc (Zn) deposition. However, they typically suffer from sluggish ion transport kinetics and poor wettability by aqueous electrolytes, resulting in unsatisfactory electrochemical performance. Here a dehydroxylation strategy is proposed to overcome the above-mentioned limitations for polyvinyl alcohol (PVA) separators. A dehydroxylated PVA-based membrane (DHPVA) is synthesized at a relatively low temperature in a highly concentrated alkaline solution. Part of the hydroxyl groups are removed and, as a result, the hydrogen bonding between PVA chains, which is deemed responsible for the sluggish ion transport kinetics, is minimized. At 20 °C, the ionic conductivity of DHPVA reaches 12.5 mS cm⁻¹, which is almost 4 times higher than that of PVA. Additionally, DHPVA effectively promotes uniform Zn deposition, leading to a significantly extended cycle life and reduced polarization, both in a/symmetric (Cu/Zn and Zn/Zn) and full cells (Zn/NaV₃O₈). This study provides a new, effective, yet simple approach to improve the performance of ZMBs.